The present invention relates to a golf club which can control a decrease in the rebound performance on off-center hit by defining a thickness distribution of a face portion in consideration of a toe down during swing, more particularly to a golf club which can be suitably used by average golfers whose head speed is 45 to 55 m/s.
In recent years, there has been proposed a golf club head having a hollow structure comprising a face portion provided with a central thick part and a thin part surrounding the central thick part for example as disclosed in Japanese patent application publication No. JP-2010-104473-A and PCT publication No. WO 01/083049. Owing to the thin part, such a golf club has an advantage such that a decrease in the rebound of the ball on off-center hit can be controlled.
By the way, as shown in FIG. 10, due to the structure of the golf club (a), the center G of gravity of the club head (b) is positioned at a certain distance from the center line (d) of the shaft (c). Accordingly, during swing, due to the centrifugal force, the club head (b) moves closer to the swing plane. As a result, the shaft (c) is bent, and the toe b1 of the club head (b) comes down (toward the ground) when compared with the position at address. Thus, so called toe-down phenomenon is caused. With increase in the toe-down, the golf ball hitting positions vary wide in the toe-heel direction of the face. The present inventor, therefore, studied on the toe-down during swing quantitatively in relation to the reverse flex of the club, and discovered that the decrease in the rebound performance on off-center hit can be minimized by specifically defining the thickness distribution of the face portion based on the reverse flex.